Hi Paul,
You are right that the online documentation shared is older one as the version that has been shared is actually the one supplied with Aspose.Slides for Java 2.8.0. Actually, Aspose.Slides for Java 2.8.1 is hotfix and new documentation will be available with Aspose.Slides for Java 2.9.0 official release. However, I will still request our development team to provide the new API documentation before if possible.
Many Thanks,